Conversion of hydrocarbon oils



Patented Feb. 16, 1943 2,310,922 CONVERSION OF HYDROCABBON OILS PortArthur, Tex., assign- Joseph Mason Barron,

or, by mesne assignments, to The Texas Company, New York, N. Y., acorporation of Delaware Application February 18, 1941, Serial No.379,463

7 Claims.

This invention relates to a combination thermal cracking and coking andcatalytic cracking process for the production of a maximum yield of highantiknock gasoline or motor fuel.

The invention contemplates a process in which a relatively light stockis subjected to catalytic cracking, the resultant hot products of thecatalytic cracking combined with a higher boiling or residual stock toeffect the coking thereof and fractions from the vapors produced in thecoking operation subjected to thermal cracking.

In practicing the invention a crude petroleum stock is distilledtoseparate a residual stock from a lighter stock such as gas oil orkerosene which is adapted for catalytic cracking. This lighter stock issubjected to catalytic cracking and the resultant products of conversiondirected to a coking zone. In one method of operation the topped orreduced crude is introduced into a dephlegmator to dephlegmate vaporsproduced,

in the flashing of residual constituents from the thermal crackingoperation and the resultant mixture of unvaporized crude residuum andreflux condensate is passed to the coking zone for reduction to coke incontact with the hot products from the catalytic cracking operation. Theevolved vapors from the coking operation are subiected to a primarydephlegmation to obtain a heavy or tarry condensate suitable for fueloil and the dephlegmated vapors are subjected to further fractionationto separate the desired gasoline or motor fuel distillate from a higherboiling reflux condensate which is cycled to the thermal cracking zone.The products of the thermal cracking operation are separated into vaporsand residue, which residue is passed to the flashing zone, while theseparated vapors are combined with vapors from the coking operation forfractionation therewith. The tarry condensate obtained in the primarydephlegmation of the coke still vapors is either withdrawn to constitutea fuel oil product or is passed to a flashing zone for reduction todesired viscosity or flash test.

In a modification of the invention the residue from the thermal crackingoperation instead of being passed to the flashing zone is directed tothe coking zone.

In another modification contemplated by the invention the topped orreduced crude is combined with the heated stream of products from theheating coil of the thermal cracking operation and the combined productsare subjected to cracking in a reaction zone, and in this operseparatingthe ation the residue obtained in products of the thermal cracking mayeither be passed to the coking zone for reduction to coke or deliveredto the flashing zone for the produc tion of fuel 011.

For the purpose of more fully disclosing the in vention reference is nowhad to the accompanying drawing which is a flow diagram illustratingdrawing which is a flow diagram illustrating apparatus adapted for thepractice of the invention.

In the apparatus illustrated a crude oil stock, such as crude oil ortopped crude, is directed by a pump Iii to a heating coil Ii, heated byheat exchange with hot product from the system or otherwise, and ispassed thence to a tower i2 wherein separation of vapors from residuetakes place and wherein the separated vapors are subjected tofractionation. The residue is withdrawn through a line l3 in which is apump H. Condensate fractions, such as gas oil and kerosene constituents,suitable for catalytic cracking are collected in a tray l5 while anylighter ire-c tions which it is not desired to subject to catalyticcracking are passed overhead to a condenser coil 16 and receiving drumH.

The condensate from tray I! of tower i2 is withdrawn through a line "anddirected by a pump l9 to a heating coil 20 disposed in a furnace 2i andthe heated oil is passed to a catalytic cracking chamber 12 containing abed of catalytic material. Ordinarily, a plurality of catalyst chambersare used so that the catalyst may from time to time be revivified orregenerated without disturbing the continuity of the completecombination process.

The catalyst consists advantageously of a thetic silica-alumina type ofcatalyst. Various acid-treated and metal-substituted clays such as theSuper-Filtrols and acid-treated and metalsubstituted natural orartificial zeolites, such as the artificial zeolite known as Doucil maybe employed. Various metals such as uranium, molybdenum, manganese,lead, zinc, zirconium, nickel and the like, may be substituted in theclays or zeolites. Likewise, the combination of certain acid-treatedactive clays of the character of Filtrol, together with addedproportions of sin-- mine or silica or both may be employed. Alu mine.alone may be used tions. The synthetic alumina catalysts can be improvedby the addition of other constituents such as zirconium oxide ormolbdenum oxide.

The thermal cracking portion of the system includes a heating coil 23disposed in a furnace under certain condi 24 having a transfer line 25extending to a reaction chamber 26 which has a discharge line 21extending to a second reaction or separating chamber 28. Residue fromchamber 28 is withdrawn through a line 29 to a flash tower 32 whereinthe residue is flash distilled under reduced pressure. Separation ofvapors from residue takes place in the tower 32 and the residue iswithdrawn through a line 33 while the separated vapors pass into theupper sections of the tower for fractionation.

Crude residuum is directed by the pump i4 through the line i3 to anupper section of the flash tower 32 to dephlegmate the vapors therein, aresultant mixture of reflux condensate and unvaporized residuumcollecting on a tray 34. A pump 33 conducts the crude residuum mixturefrom tray 34 through a line 33 to a coking drum 31. The hot productsfrom the catalytic cracking zone 22 are discharged through a line 33communicating with line 38 so that hot products are mixed with the cruderesiduum mixture so as to be converted to coke in the coking chamber 31.

In a modification of the invention the crude residuum from the crudestripping tower instead of being introduced into the flash tower isdirected through a branch line No oi the line i3 and combined directlywith the hot products from the catalytic cracking zone for coking in thecoking chamber 31. v

The vapors from the coking drum pass through a vapor line 39 to afractionating tower 43. The vapors from the coking drum preferably passto a primary dephlegmating section 40A of the tower wherein the vaporsfrom the coking operation are subjected to a primary dephlegmation toform a heavy or tarry condensate. The dephlegmating section 40A may berefluxed with gas oil. A portion of the bottoms withdrawn from dephleg-'mator 40A may be advantageously recycled through the dephlegmator inorder to provide a flow of liquid therein to prevent coking. Bottomsfrom dephlegmator 43A may be conducted through a line 4! and thencethrough line 29 to the flash tower. Vapors uncondensed in thedephlegmating section 46A pass upwardly to a iractionating section 40Biorturther fractionation, the resultant reflux condensate beingcollected on a tray 42.

Vapors from the chamber 23 pass through a vapor line 43 to the tower 43,preferably entering the tower at a point above the trapout tray 42, andthe combined vapors from the chamber 23 and from the dephlegmatingsection 40A are subjected to fractionation in i'ractionating section40B. Reflux condensate is withdrawn from tray 42 by a pump 4-4 anddirected through a line 43 to the heating coil 23. The overhead vaporsfrom tower 40 pass to a condenser 43 and the distillate is collected ina receiving drum or gas separator 41.

The overhead distillate from the flash tower 32 passes to a condensercoil 43 and the distillate is collected in a receiving drum 43 or gasseparator. The flash distillate is withdrawn through a line 50. Thisdistillate consists essentially of thermally cracked constituents and itmay with advantage be directed to the catalytic cracking zone. A pump 3!having an intake line communicating withline B and having a dischargeline 52 is provided for directing a portion or all of the flashdistillate to the heating coil of the catalytic cracking unit. Ifdesired, a portion or all of the flash distillate may be refluxed ineither or both oi. the fractionating sections 40A and 43B of tower 40and in this way flashed constituents will be included in the cyclecondensate passing to the thermal cracking zone.

In a modification of the invention the residue 5 withdrawn from chamber23, instead of being directed to the flash tower, may be directedthrough a branch line 53 of the line 29 and combined with hot productsfrom the catalytic cracking zone for coking,

In another modification oi the invention the crude residuum from thecrude stripping tower passing through line l3 may be directed through abranch line 34 and combined with the hot products passing from theheating coil 23 and the mixture subjected to cracking in the reactionchambers, and in this method of operation the residue separating out inchamber 23 may either be passed through the line 3| to the flash toweror through line 33 to the coking chamber.

In practicing the invention the crude oil stock is distilled andfractionated into the fractions desired. A fraction suitable forcatalytic cracking is heated in the heating coil 23 to a temperaturesuflicient to maintain the desired temperature in the catalyst case 22.Thus, the oil in transit through the coil 23 is vaporized and is heatedsufllciently to maintain cracking temperatures of the order of 850 F. to1050 F. and preferably temperatures of 910 F. to 1000' I". in the socatalyst case 22. The topped or reduced crude,

as it comes from the stripping tower at temperatures of the order of 600F. to 750' 1",, is com bined directly with the hot products dischargingfrom the catalyst case and the mixture is passed as to the coking drumfor coking, or the topped or reduced crude may be introduced into the dophlegmator oi the flashing unit and the resultant mixture of heavyreflux condensate and unvaporized residue is combined with the hotproducts from the catalyst case for coking in the coking chamber. ator43 is subjected to thermal cracking in the heating coil 23 and reactionchambers 23 and 23 under the usual temperatures suitable for thermalcracking and under superatmospheric pressures, usually in excess of 100lbs. and preferably of the order of 400 to 600 lbs. The so-calledlow-liquidlevel or no-liquid-level conditions are preferably maintainedin the reaction chambers 23 and 23, the residue being rapidly withdrawnfrom the chamber 23 so as to prevent the accumulation of liquid.Distillate comprising a mixture or gasoline constituents formed in thecatalytic cracking, thermal cracking and coking is collected in thereceiver I1.

The cracked residue withdrawn from chamber- 23 is normally passed to theflashing tower for flash distillation to produce a fuel oil product ofdesired flash and viscosity, or to produce a high viscosity productadapted for the preparation or a fuel 011 product by cutting back with asuitable high flash condensate stock. While it is within the purview oi!the invention to combine the residue i'rom the thermal crackingoperation with the hot products from the catalytic cracking operation toeii'ect coking, it is generally preferable to utilize the thermallycracked residue for the production of fuel oil, while reducing thetopped or reduced crude to coke by being admixed with the catalyticallycracked products. The cracked residue, particularly when it consistsessentially of polymers produced by cracking, is better adapted for fueloil than the crude oil residue, since the cracked residue ischaracterized by having a higher speciflc gravity and a higher calo-Cycle condensate from the fraction-- riflc value for a given viscositythan the uncracked residual stock, and furthermore, the coking of thetopped or reduced crude will ordinarily produce greater yields ofgasoline and intermediate stock adapted for further cracking intogasoline with relatively less gas production than is the case in cokingthe cracked residue. There is, consequently, a particular advantage inac complishing the reduction of the topped or reduced crude to coke bymeans of the hot prod note from the catalytic cracking operation whilereserving the residue from the thermal cracking operation for theproduction of fuel oil. The heavy tarry condensate which is produced inthe primary dephlegmation o! the vapors from the coking drum is alsowell adapted for the production of fuel oil and may be withdrawn as aseparate product or passed to the flashing zone together with theresidue from the thermal crack- 7 ing operation In the operation inwhich the crude residuum is passed through line It to be combined withthe hot products from the cycle condensate heating or cracking coil 23the crude residue may be withdrawn from the crude stripping tower attemperatures of 600 1!. to 750 F. and combined with the hot productsfrom the heating coil which ordinarily leave the coil at temperatures ofthe order of 900 F.-1000 F. In this operation the residue withdrawn fromthe reaction chamber 28 may be converted to coke by being combined withthe hot products from the catalytic cracking operation, or this residuemay be passed to the flashing zone in which case the products from thecatalytic cracking zone may be reduced to coke in the coking zonewithout the addition thereto the thermally cracked residue.

In an example of the invention virgin gas oil of 30 A. P. I. gravity ischarged to the heating coil of the catalytic cracking unit at a rate of150 barrels per hour. The oil is heated to a tem perature of 1000" F.and passed into the catalyst case which is maintained under a pressureor lot) lbs. per square inch. Topped crude of 26 A. P. I. gravity ispreheated by heat exchange with flashed vapors, with vapors from thecrude fractionator and with vapors from the pressure trac tionator ofthe thermal cracking unit and it is further heated by furnace heat to atemperature of about 650 F. and is then introduced into thedephlegmating section of the flashtower. The resultant mixture of refluxcondensate and un= vaporized crude residuum is combined with the hotproducts discharging from the catalyst case and subjected to coking inthe coking drum. In

the thermal cracking operation the cycle condensate is heated to atemperature of 950 F. in the heating coil and the reaction chambers aremaintained under 400 lbs. pressure with a temperature of 910 F. in theflrst reaction chamber, while the residue is discharged from the secondraction chamber at a temperature of 850 F. This residue is passed to theflashing chamber in which a pressure of about to lbs. is maintained.Pressures approximating 100 lbs. are maintained in the coking drum andin the pressure fraction ator in which the vapors from the thermal cracking and coking operations are fractionated. Vapors leave the coking drumat temperatures of about 840 F. to 850 F. and vapors pass from thesecond reaction chamber at a temperature of 850 F. to 870 F. to theiractionator.-

While I have described a particular embodiment of my invention forpurposes of illustration, it should be understood that'variousmodifications and adaptations thereof which will its obvious to oneskilled in the art, may he made within the spirit of the invention asset forth in the appended claims.

I claim:

1. In the conversion oi hydrocarbon oils the process that comprisesseparately distilling crude petroleum to separate residual constituentsfrom lighter components, subjecting such straight ri lighter componentsto catalytic cracking, comhln ing residual constituents from the crudepetroleum with hot products from the catalytic cracking operation andconverting the admixed products to coke in a coking zone, subjecting theevolved vapors from the coking zone to a primary dephlegmation to form atarry condensate adapted for fuel oil, passing the dephlegmated vaporsto a fractionating zone wherein the vapors are fractionated to separatea reflux condensate from lighter products, directing said reflux condensate to a thermal cracking zone wherein the oil is subjected tocracking conditions of tem perature and pressure, separating theresultant cracked products into vapors and residue and combining theseparated vapors with vapors from the coking operation, after saidprimary dephleg mation thereof, for fractionation in said true tionatingzone.

2. In the conversion of hydrocarbon oils the method oi treating a crudepetroleum residual charging stock and a straight-run condensate stockthat comprises subjecting the condensate stock to catalytic cracking,combining the residual stock with hot products from the catalyticcracking operation and converting the admixed products to coke in acoking zone, subjecting the evolved vapors from the coking zone to aprimary dephlegmation to form a tarry condensate, pawing thedephlegmated vapors to a fractionatiug zone wherein the vapors arefractionated to gap arate a reflux condensate from lighter products,directing said reflux condensate to a thermal cracking zone wherein theoil is subjected to cracking conditions of temperature and pressure,separating the resultant cracked products into vapors and residue, andcombining the separated vapors with vapors from the cokingoperation,after said primary dephlegmation thereol, tor fractionation in saidfractionating zone.

3. In the conversion of hydrocarbon oils the process that comprisesdistilling crude mtroleum to separate a residue from a lighter fraction,sub Jectlng the lighter fraction to catalytic cracking, dephlegmatingvapors from a flashing zone with said residue to form a resultantmixture of reflux condensate and unvaporized residue, combining saidmixture with hot products from the catalytic cracking operation andconverting the admixed products to coke in a coking zone, subjectingevolved vapors from the coking zone to a psi mary dephlegmation to forma tarry condte, passing the dephlegmated vapors to a iractionat ing zonewherein the vapors are fractionated to separate a reflux condensate fromlighter prod ucts, directing said reflux etc to a thermal cracking zonewherein the oil is subjected to cracking conditions oil temperature andpressure, separating the resultant cracked products vapors and residue,passing the separated vapmc to said fractionating zone and directing thesepa rated residue and said tarry condensate to said flashing zone.

4. In the conversion of hydrocarbon oils the method of treating aresidual stock and a will densate stock that comprises subjecting thecdensate stock to catalytic cracking, dephlegmating vapors from aflashing zone with the residual stock to form a resultant mixture ofreflux condensate and unvaporized residue, combining said mixture withhot products from the catalytic cracking operation and converting theadmixed products to coke in a coking zone, subjecting the evolved vaporsfrom the coking zone to a pimary dephlegmation to form a tarrycondensate, passing the dephlegmatetl vapors to a fractionating zonewherein the vapors are fractionated to separate a reflux condensate fromlighter products, directing said reflux condensate to a thermal crackingzone wherein the oil is subjected to cracking conditions of temperatureand pressure, separating the resultant cracked products into vapors andresidue, passing the separated vapors to said fractionating zone anddirecting the separated residue and said tarry condensate to saidflashing zone.

5. In the conversion of hydrocarbon oils the method of treating aresidual stock and a condensate stock that comprises subjecting thecondensate stock to catalytic cracking in a catalytic cracking zone,dephlegmating vapors from a flashing zone with the residual stock toform a resultant mixture of reflux condensate and unvaporized residue,subjecting the dephlegmated vapors to condensation, directing resultantcondensate to the catalytic cracking zone, combining the residual stockmixture, obtained in dephlegmating the flashed vapors, with hot productsfrom the catalytic cracking operation and converting the admixedproducts to coke in a coking zone, subjecting the evolved vapors fromthe coking zone to a primary dephlegmation to form a tarry condensate,passing the dephlegmated vapors to a iractionating zone wherein thevapors are fractionated to separate a reflux condensate from lighterproducts, directing said reflux condensate to a thermal cracking zonewherein the oil is subjected to cracking conditions of temperature andpressure, separating the resultant cracked products into vapors andresidue, passing the separated vapors tosaid rractionating zone anddirecting the residue separated irom the thermally cracked products tosaid flashing zone.

6. In the conversion of hydrocarbon oils the method of treating aresidual stock and a condensate stock that comprises subjecting thecondensate stock to catalytic cracking, dephlegmating vapors from aflashing zone with the residual stock to form a resultant mixture oireflux condensate and unvaporized residue, combining said mixture withhot products from the catalytic cracking operation and converting theadmixed products to coke in a coking zone, subjecting the evolved vaporsfrom the coking zone to a primary dephlegmation to form a tarrycondensate, directing the tarry condensate to said flashing zone,passing the dephlegmated vapors to a fractionating zone wherein thevapors are fractionated to separate a reflux condensate from lighterproducts, directing said reflux condensate to a thermal cracking zonewherein the oil is subjected to cracking conditions of temperature andpressure, separating the resultant cracked products into vapors andresidue, passing the separated vapors to said fractionating zone andpassing the separated residue to said coking zone for conversion to coketherein.

7. In the conversion of hydrocarbon oils the process that comprisesdistilling crude petroleum to separate a residue from a lighterfraction, subjecting the lighter fraction to catalytic cracking, passingcycle condensate to a heating zone wherein it is heated to a crackingtemperature, combining said residue with the heated products from saidheating zone and subjecting the commingled products in a thermalreaction zone to cracking temperature under superatmospheric pressure toeffect cracking, separating the resultant cracked products of thethermal cracking into vapors and residue, passing the separated vaporsto a fractionating zone wherein the vapors are fractionated to separatea reflux condensate from lighter products, directing said refluxcondensate to said heating zone as said cycle condensate, combining theresultant hot products from the catalytic cracking operation with theresidue separated from the thermally cracked products and converting theadmixed products to coke in s. coking zone, subjecting the evolvedvapors from the coking zone to a primary dephlegmation to form a tarrycondensate and passing the dephlegmated vapors to said iractionatingzone.

JOSEPH MASON BARRON.

